arm64: dts: rockchip: Add NanoPC-T4 IR receiver

In common with most Rockchip reference designs, NanoPC-T4 has a passive
IR receiver connected to PWM3. In lieu of a specialised driver for
PWM-based IR pulse measurement, running the pin as a GPIO with the basic
driver works perfectly well.

Signed-off-by: Robin Murphy <robin.murphy@arm.com>
Signed-off-by: Heiko Stuebner <heiko@sntech.de>